1. Field of the Invention
This invention relates to electrochemical double-layer capacitors, and more particularly to an improved enclosure or casing therefor.
2. Description of the Prior Art
Electric or electrochemical double-layer capacitors make use of an electric double layer formed at an interface between each polarization electrode and an electrolyte, and are usually comprised of a pair of polarization electrodes each made of carbon which is usually applied to a conductive metal plate and a spacer or separator impregnated with an electrolyte solution, the spacer being interposed between the pair of electrodes which are facing each other.
The electrochemical double-layer capacitor of the just-mentioned type has a much greater electrostatic capacity than ordinary electrolytic capacitors and is rapidly chargeable in a manner similar to electrolytic condensers or capacitors, so that it has become of major interest as a substitute for known secondary cells or batteries for its application to power units for back-up or stand-by purposes.
In the manufacture of the electrochemical double-layer capacitor, it is common practice to use as an enclosure or casing a combination of a metal container shaped by press work and a sealing plate therefor. However, since there is a recent trend for making the thickness of the electrochemical double-layer capacitor very small from the viewpoints of its characteristic properties and applications, a relatively large proportion of production cost is occupied by the container and this container cost now presents a problem of economy.
Further, the electrochemical double-layer capacitor has an advantage that a large electrostatic capacity is obtained as compared with those obtained from other types of capacitors but has a disadvantage that the breakdown voltage is as low as below several volts. Thus, its application is restricted to an extent. In other words, due to the low breakdown voltage, it can not be applied to electric appliances using high voltage.
On application to such electric appliances such as those operated under high voltage, it is necessary to use a plurality of electrochemical double-layer capacitors connected in series. However, known electrochemical double-layer capacitors are not suitable for that purpose and thus there is an additional demand for development of an electrochemical double-layer capacitor having a novel enclosure construction.